Respuestas
Affirmative clauses: 1° have to can be used in all tenses: Tom had to wear a uniform last year / Tom will have to wear a uniform next year Sonia is having to wait / she may have to come back tomorrow 2° must can be used to talk about the present or the future Tom must call his mother tomorrow but it can't be used to talk about the past ( you use have to) III) Interrogative clauses: Do you have to leave now? / Must you leave right now? IV) Negative clauses: The negative form of must and the negative form of have to are very different in meaning. 1° must not / mustn't is used to say that something is not allowed. Children mustn't play with fire. / Passengers must not talk to the driver. / Visitors mustn't smoke. 'must not' can't be used to talk about the past, you use another structure. example: We were not allowed to park near the museum. 2° don't have to means that there is no obligation to do something, but you can do it if you want. You don't have to drink alcohol, you can have a soft drink. She doesn't have to arrive before 9.